Abrasive tool



Patented May -27, 194i Paul L. Kuzmick, Clifton, N. 1., asslgnor to J. K. Smit & Sons, Inc., New York, N. Y., a corpora- I tion of New York No Drawing. Application July 28, 1939,

Serial N0. 287,003

Claims.

My invention relates to abrasive tools comprising a bonded mixture of metal particles, abrasive particles and a non-metallic bond.

Among the objects of my invention, but without regard to the order of their importance; are:

1. The production of an abrasive tool which is a highly heat resistant and.- which conducts fric tional heat rapidly away from its working face because of its-high metallic content.

' 2. The production of an abrasive tool the porosity of which can be readily controlled, which turing and of oxidizing the expensive abrasive during the process of manufacture of the tool.

4. The production of an abrasive tool in the manufacture of which, if desired, a small percentage of lead, tin or other very ductile metal can be added to impart a greasy or lubricating efiect, thus increasing the ease and speed of cut,

and by the same token loosened abrasive particles easily become absorbed, thereby realizing -more work out of a given amount of abrasive.

5. The production of an abrasive tool which in the course of its manufacture may be readily molded to a metallic support, as my improved tool possesses excellent heat conducting properties. By reason of this fact frictional heat developed at the working face flows therefrom through the 7 tool structure to its support, where it is readily dissipated.

6. The production of an abrasive tool capable of. producing better finishes than'possible withprior tools, owing to the high metal content of my improved tool. 7. The production of abrasive tools the hardness of which may be varied by varying the type of metal employed in their construction.

More specifically my invention is directed to abrasive tools suitable for grinding-lapping, poland finishing metals, my improved tool comprising particles of one or more metals, such non-metallic bond of which a resinoid bond is an example; Suchphenol-formaldehyde prep- .as 'one or more metal powders, abrasivev granules suchas diamond, boron carbide, etc., and a strong arations known commercially as Durite #278,?"

Bakelite #BR2417 and Durez #9540," have. proven very successful in the practice of my invention. V a w The metals-usable in the production of my improved. tools may vary depending upon the characteristics desired in the finished product. For example, in some instances I may employ powdered copper alone, but where circumstances demand I may add powdered tin, powdered iron, powdered nickel or other powdered metal.

The amount of abrasive employed is variable,

but in all cases the metal, by weight, exceeds the abrasive.

The amount of bonding material employed may be varied also, but on the average the bond percentageranges from 10% to 30% by weight. I might mention that the bond percentage may at times be higher or lower than the range just mentioned. For example, where aluminum powder is used which has a specific gravity of 2.56 as compared with 8.82 for copper, it will be apparent that the bond percentage will be high, it may even be as high as 50% by weight. on the other hand, when coarse metal powders are employed, the percentage of bonding material is low, because these coarse metal particles approach the specific' gravity of. solid metal thus having less volume by weight than fine particles, even in some instances as low as 4.50% by weight.

In making up my improved tool the metal pow der, abrasive and binder are molded under pressure. The' binder is heat cured, the temperature 4 used being below the fusing point of the metal powder in all cases. The pressure employed in most instances is relatively low, from 1000 to 4000 pounds per square inch, thereby effectively avoid.- ing injury to the abrasive particles. The tem-.

perature necessary for curing the binder is also low, as above indicated, around 320 F. which eflectively eliminates oxidation ofthe abrasive and is well below the fusing point of the metals,

.so that'the mixture in the finished tool will be metal particles, abrasive particles and a strong non-metallic binder.

As above mentioned, the mesh size of the metal particles employed may be varied, the metal par even higher. For the purposes of this application metal powders of 200 mesh and upwards are fine powders, while powders below 200 mesh are to be considered coarse powders.

It has been mentioned above that the porosity of my abrasive tool is controlled. This may be realized by employing a. closing type of mold and regulating the amount of material employed in both pressing and curing. For example, I may in one instance obtain a density of. approximately 65 grams per cubic inch. adding more'material to the mold if a denser structure is desired.

Porosity may further be controlled by varying the mesh size of the metal particles. A low pressure and coarse particles gives a. mass containing many voids as compared with the results obtained when using finer powder. A very porous structure is sometimes desirable where clearance is desired for the grinding chips or for carrying more lubricant to the work and freer cutting qualities.

I have obtained excellent results employing the following formulae:

Example A Per cent by weight Resin bond 10.73 Fine copper powder (200 mesh and upwards) 32.13 Fine tin powder (200 mesh and upwards)..- 32.14

#2 diamond powder (240-300 mesh) 25.00

Example B Per cent by weight Resin bond 9.90 Fine copper powder (200 mesh and upwards) 29.65 Fine tin powder (200 mesh and upwards) 29.65 #2 diamond powder (240-300 mesh) 30.80

Example C Per cent by weight Resin bond 4.41 350 mesh copper powder 4.41 60-120 mesh copper powder 66.14 240-300 mesh diamond powder 24.99

The curing cycles normally run from 5 to minutes at 330 F. when curing under pressure and employing resin bond in a dry state. I may use a plasticizer, however, and press cold in which event a different curing cycle is employed. In such case, after pressing an oven is used, employing stepped heating, starting at around 175 F., the temperature being raised by steps to around 350 F. The duration of each step depends upon the compactness desired and size of the article. A heat of 24 hours duration is suitable for small abrasive tools.

I have found that the resinoid bond hereinbefore referred to may be substituted by a plastic rubber bond, which gives' a strong integral body. This plastic rubber may be mixed with the metal powder and abrasive particles in a dough type mixer until well blended, then spread in a mold and cured in a hot press. The proportions of ingredients employed may be the same as when using a resinoid bond. This plastic rubber bond must not be confused with the common roll-mixedrubber which is unsuitable for this work.

Where a plastic rubber 'bond is used a hot press heat of minutes at 250 F. and 45 minutes at 330 F. gives excellent results. This is the procedure when pressing and curing simultaneously.

When pressing cold and curing in multiples a longer heat is used, approximately 12 hours at It will be noted that in the examples set out above the amount of metal employed is high. I have found by many'experiments and tests that I must employ a. minimum of 40% by weight of metal in making up my improved rtool, substantially less than this amount defeating my purpose. I find also that an extremely high percentage of abrasive is detrimental, inasmuch as it spreads the bond or matrix to such an extent that the tool loses many of the advantages it otherwise possesses.

. It is to be understood that changes may be made in the details of construction above described within the purview of my invention.

This application is a continuation-in-part of my copending application Serial; No. 253,741, filed January 31, 1939.

What I claim is:

1. An abrasive tool comprising finely divided particles of a plurality of metals of different degrees of hardness, abrasive granules, and a non-metallic binder, molded into an integral body, the metal particles, by weight, exceeding the abrasive granules.

2. An abrasive tool comprising finely divided particles of a plurality of metals of different degrees of hardness, abrasive granules and a resinoid binder.

3. An abrasive tool comprising copper powder, tin powder, diamond powder and a resinoid bond, substantially in the following proportions by weight:

4. An abrasive tool comprising copper powder varying from 60-120 mesh, 350 mesh copper powder, 240-300 mesh diamond powder and a resinoid bond, substantially in the following proportions by weight.

Per cent -60-120 mesh copper powder 66.14 350 mesh copper powder 4.41

240-300 mesh diamond powder 24.99 Resinoid bond 4.41

5. An abrasive tool comprising metal particles and abrasive particles bonded by a plastic rubber heat cured bond, the metal particles by weight exceeding the abrasive particles.

PAUL L. KUZM ICK. 

